Abstract: Magnetic recording elements containing substantially transparent magnetic recording layers which exhibit excellent magnetic recording and reproducing characteristics. Such elements contain a support and a transparent magnetic recording layer. The recording layer has a thickness up to about 5 microns and contains acicular, magnetizable particles having an average width of less than about 0.06 micron and an average length up to about 1 micron. These particles are substantially homogeneously dispersed in a medium that comprises a binder and has a refractive index which is substantially the same throughout the thickness of the magnetic recording layer. The concentration of the binder is at least about 10 parts per 100 parts, by weight, of the particles and is up to about 30 parts, by weight, for particles having an average length of at least about 0.06 micron and up to about 40 parts, per 100 parts, by weight, for particles having an average length of less than about 0.06 micron.

Abstract: A process of preparing magnetic recording elements containing substantially transparent magnetic recording layer which exhibit excellent magnetic and reproducing characteristics is as follows:(a.) forming a substantially homogeneous dispersion of acicular magnetizable particles in a medium comprising a solution of substantially transparent binder in solvent using particles having an average width of less than about 0.06 micron and an average length up to about 1 micron; the concentration of the binder being at least about 10 parts per 100 parts, by weight, of the particles; up to about 30 parts, by weight, for particles having an average length of at least about 0.06 micron and up to about 40 parts, by weight, for particles having an average length of less than about 0.06 micron,(b.) coating a support with the dispersion in an amount sufficient to provide a final dry layer thickness up to about 5 microns,(c.) removing substantially all solvent from the layer and(d.

Abstract: A process for preparing acicular gamma ferric oxide (maghemite) crystals exhibiting excellent magnetic recording properties is disclosed. These acicular gamma ferric oxide crystals are new materials and can be used in magnetic media such as magnetic tapes to obtain a low level of white noise without sacrificing other electroacoustic properties. The crystals are basic in character, contain alkali metal ions and have an acicularity ratio of at least 15, often 15 to 40. These crystals are prepared under very carefully controlled reaction conditions, as more fully described in the following specification. In general, however, the process involves (1) reacting ferrous salt with a stoichiometric excess of an alkali hydroxide under non-oxidizing conditions and at a temperature below about 60.degree. C.